Step pipettes are known, which have a piston movable in a cylinder, a longitudinal pinion rack in a piston rod, a striker bearing against the pinion rack by the force of a spring as well as actuator for the striker, by means of which actuator the striker is forced to push the pinion rack drawn upwards and thereby also the piston by a desired distance downwards shorter than the entire moving distance of the piston. In the publications FI-60137 (corresponds to GB-2045641) and FI-77166 (corresponds to WO 84/04056), such pipettes are described, which additionally have a filling rack connected to the piston rod by means of a pinion, which filling rack is pressed to draw the piston to its upper position.
One problem in connection with e.g the above-mentioned step pipettes has been the fact that the last dose to be injected out often remains incomplete, since the pinion rack is no longer capable of transferring by the entire desired distance.